Dark and blurry

I am somewhat new to cameras, but took what I thought could be a really cool picture, but although the water looks really good, the people do not. Is there anything that can be done, perhaps in Photoshop to make the people sharper?

I like to use the shadow/highlight. Adjust the amount sliders to bring up the shadow detail and you can also make some adjustment in th highlight section, to keep some of the detail in the whites...but I don't think you will need much of that. Then you can use layers or curves to make further adjustments.

I definitely would've used a flash, but the water in the background then became a dull and gloomy red. Is there a way at night to to use the flash and still get the white and sort of glowing effect seen above?

With my camera & flash, I would have put the camera into manual mode...and set the aperture to match the flash setting. This should give proper exposure for the girls. Then I would set the shutter speed to something slow, this would allow time for the background to be recorded. There might be some color issues (white balance), depending on how the fountains are lit.

Well, if we are talking about the built-in flash on a DSLR...then it should automatically be set to match the exposure setting...but with most you can also adjust the flash exposure compensation (FEC).

I have a hot-shoe accessory flash (which I must set), but basically the principle is the same. You want to expose the subject with the flash, and expose the back ground with ambient light by keeping the shutter open longer.